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73 lines
2.2 KiB
Python
73 lines
2.2 KiB
Python
"""
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MP3 → Opus 预转码服务
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将 MP3 音频转为 Opus 帧列表（JSON + base64），供 hw_service_go 直接下载播放，
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跳过实时 ffmpeg 转码，大幅降低首帧延迟和 CPU 消耗。
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Opus 参数与 hw_service_go 保持一致：16kHz, 单声道, 60ms/帧
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"""
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import base64
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import json
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import logging
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import subprocess
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import opuslib
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logger = logging.getLogger(__name__)
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SAMPLE_RATE = 16000
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CHANNELS = 1
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FRAME_DURATION_MS = 60
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FRAME_SIZE = SAMPLE_RATE * FRAME_DURATION_MS // 1000 # 960 samples
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BYTES_PER_FRAME = FRAME_SIZE * 2 # 16bit = 2 bytes per sample
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def convert_mp3_to_opus_json(mp3_bytes: bytes) -> str:
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"""
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将 MP3 音频数据转码为 Opus 帧 JSON。
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流程: MP3 bytes → ffmpeg(PCM 16kHz mono s16le) → opuslib(60ms Opus 帧)
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Returns:
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JSON 字符串，包含 base64 编码的 Opus 帧列表
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"""
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# 1. ffmpeg: MP3 → PCM (16kHz, mono, signed 16-bit little-endian)
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proc = subprocess.run(
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[
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'ffmpeg', '-nostdin', '-loglevel', 'error',
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'-i', 'pipe:0',
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'-ar', str(SAMPLE_RATE),
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'-ac', str(CHANNELS),
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'-f', 's16le',
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'pipe:1',
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],
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input=mp3_bytes,
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capture_output=True,
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timeout=120,
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)
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if proc.returncode != 0:
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stderr = proc.stderr.decode(errors='replace')
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raise RuntimeError(f'ffmpeg 转码失败: {stderr}')
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pcm = proc.stdout
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if len(pcm) < BYTES_PER_FRAME:
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raise RuntimeError(f'PCM 数据过短: {len(pcm)} bytes')
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# 2. Opus 编码：逐帧编码
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encoder = opuslib.Encoder(SAMPLE_RATE, CHANNELS, 'audio')
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frames = []
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for offset in range(0, len(pcm) - BYTES_PER_FRAME + 1, BYTES_PER_FRAME):
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chunk = pcm[offset:offset + BYTES_PER_FRAME]
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opus_frame = encoder.encode(chunk, FRAME_SIZE)
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frames.append(base64.b64encode(opus_frame).decode('ascii'))
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logger.info(f'Opus 预转码完成: {len(frames)} 帧, '
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f'约 {len(frames) * FRAME_DURATION_MS / 1000:.1f}s 音频')
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return json.dumps({
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'sample_rate': SAMPLE_RATE,
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'channels': CHANNELS,
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'frame_duration_ms': FRAME_DURATION_MS,
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'frames': frames,
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}, separators=(',', ':')) # 紧凑格式，减少体积
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